Security camera systems

ABSTRACT

A security camera system is provided. Several video cameras operate in conjunction with an image display monitor, a user control and camera selector means whereby a target of interest may be followed. Each two cameras providing adjacent areas of coverage are operable to provide an overlay image portion at transition regions of a displayed image. Upon movement of the target of interest to a specified transition region of a currently displayed image provided by one video camera, the camera selection means is operable to select a second camera whereby to maintain target display continuity by the monitor.

[0001] This invention relates to security camera systems and moreespecially but not exclusively it relates to camera systems of the kindused in shopping precincts or urban centres to provide videosurveillance.

[0002] Camera systems providing video surveillance are in common use andmay comprise a large number of cameras in order to provide adequatevideo surveillance of a prescribed area. If an incident occurs, securitystaff in ‘closed circuit television’ (CCTV) control rooms, will attemptto keep a person involved in the incident, and who might be making hasteto leave the scene, within the field of view. This might involveswitching between cameras, as the person leaves the field of view of onecamera and enters the field of view of another camera or cameras, sothat the camera used is always the one which affords the best view ofthe person being observed. In practice, this can be difficult, requiringhighly trained staff who are familiar with the camera layout on aparticular site. It is therefore all too easy to lose track of a person,even on a site having good camera coverage, and this may result in theloss of vital evidence, since video surveillance data used forprosecution is typically required to be continuous in time.

[0003] It is an object of this invention to provide an improved camerasystem wherein the tracking of a person moving between areas covered bydifferent security cameras is facilitated whereby the task of securitystaff is simplified.

[0004] In accordance with a further aspect of the invention, there isprovided a security camera system comprising a plurality of videocameras, an image display monitor, a user control and camera selectormeans; wherein the cameras' images in combination can provide apredetermined overall area of coverage; wherein a target of interest canbe observed by a first video camera and an image of said target bedisplayed on the monitor; characterised in that overlap image portionsat transition regions of a displayed image are provided by two adjacentcameras, each such transition region being displayed as a ‘button’region by the image display; wherein there are a plurality of such‘button’ regions being arranged about or surround a central area in animage in a field of view; wherein, upon movement of the target to atransition region, the user control is operable to select the ‘button’region of an image displayed, whereby to select a second camera and toemploy video signals from the second video camera to maintain targetimage continuity.

[0005] The user control may comprise a mouse or a like device to controla cursor which is operable to indicate when the target has moved to animage transition region. Alternatively or additionally a touch sensitivescreen may be provided.

[0006] The user control may be used to select a transition regiondisplayed by the image display monitor, from a plurality of such regionswhich are arranged to surround an image displayed, and which are alsoarranged within the image, the transition region selected indicating animage region of a currently displayed image approached by a target, independence upon which transition region selection, video signals fromanother of the video cameras are used thereby to maintain target displaycontinuity by the monitor.

[0007] Conveniently the user control includes a CPU, which is operableto store data including, in respect of each camera, the pixel positionsof the lines at which transitions occur, and the identity of the camerato be selected at that transition. The data stored in the CPU mayinclude, for example, in respect of each camera: image centre data,focal length data, and distortion parameters. At least some of thecameras may be fixed and/or at least some of the cameras may bepan-tilt-zoom (PTZ) cameras. The CPU may include image processingsoftware which operates to recognise the character of an image bycomparing it for correspondence with a plurality of stored referenceimages, in dependence upon which comparison, the CPU operates for cameraselection.

[0008] The CPU may include image processing software which operates torecognise a character in an image by comparing key features of the imagefor correlation with key features in a plurality of stored referenceimages in dependence upon which comparison the CPU operates for cameraselection.

[0009] In one embodiment the features along one or more co-ordinates ofan image may be compared for correlation with the features of one ormore corresponding co-ordinates of a reference image.

[0010] The video camera may be a thermo-sensing camera such as aninfra-red camera.

[0011] In accordance with a further aspect of the invention, there isprovided a security camera system, a method of operating a securitycamera system comprising a plurality of video cameras, an image-displaymonitor, a user control and camera selector means; wherein the cameras'images in combination can provide a predetermined overall area ofcoverage; wherein a target of interest can be observed by a first videocamera and an image of said target be displayed on the monitor; whereinoverlap image portions at transition regions of a displayed image areprovided by two adjacent cameras, each such transition region beingdisplayed as a ‘button’ region by the image display; wherein there are aplurality of such ‘button’ regions being arranged about or surround acentral area in an image field of view; wherein, upon movement of thetarget to a transition region, the user control is operable to selectthe ‘button’ region of an image displayed, whereby to select a secondcamera and to employ video signals from the second video camera; themethod comprising the steps of: observing a target of interest displayedas an image on the monitor; characterised in that upon movement of thetarget to a transition region, operating the camera selection meanswhereby an image from a second camera is displayed, whereby target imagecontinuity may be maintained. The user control may comprise a mouse or alike operative device operable to control a cursor which can be used totrack the target and to indicate when it has moved to an imagetransition region.

[0012] One embodiment of the invention will now be described by way ofexample only with reference to accompanying drawings wherein;

[0013]FIG. 1, is a schematic block diagram of a security camera systemusing fixed cameras and,

[0014]FIG. 2, is a schematic block diagram of a security camera systemusing fixed cameras and PTZ cameras wherein parts corresponding to thoseshown in FIG. 1 bear the same numerical designations.

[0015] Referring now to FIG. 1, an exemplary security camera system isshown, of the kind used in shopping precincts or urban centres toprovide video surveillance comprises a plurality of fixed securitycameras 1, 2, 3, 4, which are arranged to feed their respective videosignals to a camera matrix 5. The camera matrix 5, serves as a videocamera selector, to select the signals from one of the cameras 1, 2, 3,4, for display on the screen of an image display monitor 6, which isoperatively associated with a user interaction device 7. The device 7,might conveniently comprise a mouse or the like which can be used tomove a cursor 8, around an image display 9, on the display monitor 6.Instead of there being a memory means associated with the matrix(control selection means), there is provided a separate CPU whichreceives signals from the camera matrix relating to all the signals fromthe cameras. The camera matrix 5, is controlled by the CPU in which datais retained relating to a fixed field of view afforded by each of thecameras 1, 2, 3, 4, and the position of the cursor 8. In operation, atarget person, for example, may be visually followed by an operatoracross a current image field of view and when the target approaches anedge of the field of view, the device 7 may be used to ‘mark’ the spotwith the cursor 8, for example by ‘clicking’ on the boundary. Dataidentifying the marked spot together with data appertaining to eachavailable camera image is then processed in the CPU in order to selectthe most suitable camera to feed the monitor 6.

[0016] In an alternative embodiment the image displayed may besurrounded by ‘button regions’ 11, the ‘button region’ (or regions)adjacent to a spot whereat a target approaches the limit of an imagebeing selected using the cursor 8, and the device 7, in order to provideinformation for the CPU to facilitate selection of an appropriate one ofthe cameras 1, 2, 3, or 4 for the image display 9.

[0017] In a still further embodiment, the screen may be equipped with atouch sensitive screen, whereby the camera is selected following theplacing of a finger, for example, upon a touch sensitive portion of thescreen.

[0018] Referring now to FIG. 2, in an alternative arrangement PTZcameras 12, 13, and 14, are used in addition to the fixed cameras 1, 2,3, 4. In this arrangement data is stored in the CPU appertaining tovarious parameters relating to the image produced by each of the PTZcameras 12, 13, 14, to facilitate image processing in the CPU in orderto determine the relationship of each image, to other images, to theoverall display coverage and to the cursor and/or button positions,whereby a determination in the CPU of the most appropriate camera to useis facilitated.

[0019] Considering now some applications, it will be appreciated that asystem according to this invention would enable security staff to tracka suspect target through the images provided by a set of video cameras,using both PTZ cameras and/or fixed cameras or, indeed, to have a systemhaving logic operable to track an identified target. It is apparent thatwith fixed cameras, the problem is comparatively easily solved byknowledge of the transition regions in each camera where the subjectleaves the field of view, and of the camera on which that region cannext be seen.

[0020] Alternatively, if a point in one image is selected, all othercameras on which that point can be seen, could be displayed, forexample, as windows on a PC display. The security staff would then becapable of tracking a target individual by ‘clicking’ on the currentimage view at a point where the target individual goes off the edge ofthe scene, so as to prompt the provision a fresh display provided by thebest one of the other cameras to which the target is visible.

[0021] For PTZ cameras the problem is somewhat more complex, but isnevertheless soluble. In existing camera installations, it is unlikelythat the PTZ cameras will have feedback of the values of pan, tilt andzoom available to the PC. This information, or some equivalentinformation, is necessary to determine on which new cameras a targetwill be visible when leaving the field of view of a current camera. Thisinformation can however be measured, as herein before explained, byusing image processing. This method requires comparison of a currentimage with a set of stored reference images to determine where thetransition regions occur in the current image. This could be done inreal-time whilst a camera was being moved by operation of it joystickcontrol, to determine its current PTZ parameters. With the use of asmart CPU, the functions of a user control could be reduced to that ofselecting a target.

1. A security camera system comprising a plurality of video cameras(1-4), an image display monitor (6), a user control (2) and cameraselector means (5); wherein the cameras' images in combination canprovide a predetermined overall area of coverage; wherein a target ofinterest can be observed by a first video camera and an image of saidtarget be displayed on the monitor; characterised in that overlap imageportions at transition regions of a displayed image are provided by twoadjacent cameras, each such transition region being displayed as a‘button’ region (11) by the image display (9); wherein there are aplurality of such ‘button’ regions being arranged about or surround acentral area in an image in a field of view; wherein, upon movement ofthe target to a transition region, the user control is operable toselect the ‘button’ region of an image displayed, whereby to select asecond camera and to employ video signals from the second video camerato maintain target image continuity.
 2. A security camera system asclaimed in claim 1, wherein the user control comprises a mouse or thelike operative device operable to control a cursor (8) which can be usedto track the target and to indicate when it has moved to an imagetransition region.
 3. A security camera system as claimed in claim 1wherein the user control comprises a touch sensitive screen.
 4. Asecurity camera system as claimed in any preceding claim, wherein theuser control includes a CPU and wherein the CPU is operable to storedata including, for example, in respect of each camera: image centredata, focal length data, and distortion parameters, and x,y,z, and panand tilt data.
 5. A security camera system as claimed in any precedingclaim, wherein at least some of the cameras are fixed.
 6. A securitycamera system as claimed in any preceding claim, wherein at least someof the cameras are PTZ cameras.
 7. A security camera system as claimedin claim 6, wherein the CPU includes image processing software for PTZcameras, which operates to recognise the character of an image bycomparing it for correspondence with a plurality of stored referenceimages, in dependence upon which comparison the CPU operates for cameraselection.
 8. A security camera system as claimed in claim 7, whereinthe CPU includes image processing software which operates to recognisethe character of an image by comparing key features of the image forcorrespondence with key features in a plurality of stored referenceimages in dependence upon which comparison the CPU operates for cameraselection.
 9. A security camera system as claimed in claim 8, whereinkey features along one or more co-ordinates of an image are compared forcorrespondence with the key features along one or more correspondingco-ordinates of a reference image.
 10. A security camera system asclaimed in claim 6, wherein the data stored in the CPU includes inrespect of each camera, the pixel positions of the lines at whichtransitions occur, and the identity of the camera to be selected at thattransition.
 11. A security camera system as claimed in any precedingclaim wherein the video camera is an infra-red camera.
 12. A method ofoperating a security camera system comprising a plurality of videocameras (1-4), an image display monitor (6), a user control (7) andcamera selector means (5); wherein the cameras' images in combinationcan provide a predetermined overall area of coverage; wherein a targetof interest can be observed by a first video camera and an image of saidtarget be displayed on the monitor; wherein overlap image portions attransition regions of a displayed image are provided by two adjacentcameras, each such transition region being displayed as a ‘button’region (11) by the image display (9); wherein there are a plurality ofsuch ‘button’ regions being arranged about or surround a central area inan image field of view; wherein, upon movement of the target to atransition region, the user control is operable to select the ‘button’region of an image displayed, whereby to select a second camera and toemploy video signals from the second video camera; the method comprisingthe steps of: observing a target of interest displayed as an image onthe monitor; characterised in that upon movement of the target to atransition region, operating the camera selection means whereby an imagefrom a second camera is displayed, whereby target image continuity maybe maintained.
 13. A method according to claim 12, wherein the usercontrol comprises a mouse or the like operative to control a cursor (8)which is operable to track the target and to indicate when it has movedto an image transition region.
 14. A method as claimed in claim 12wherein the user control comprises a touch sensitive screen.